共查询到20条相似文献,搜索用时 93 毫秒
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文章简要回顾了真空中激光加速电子的研究进展,着重介绍了真空俘获加速电子的动力学特点和物理机制.出现俘获加速(capture and acceleration scenario,CAS)的经典物理机制是聚焦激光束的衍射效应导致光波沿俘获电子轨迹的有效相速度减慢,以致电子有可能被长时间俘获在加速相位中并从激光场获得足够多的能量.CAS出现需要的入射动量的相空间不小,而且在实验上可以达到.此外,最佳入射动能对激光强度并不敏感,在小角入射时大约在10—20MeV.研究发现,CAS出现需要的激光场强相当高,电子获得的能量在电子进入CAS通道时急剧上升.此外文章还介绍了有质动力加速模型的特点和机制、附加磁场的加速机制. 相似文献
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使用粒子模拟程序对30 fs超短超强激光在均匀与抛物型两种密度分布等离子体中的传输, 以及在稳定传输状态下尾场的电子注入与加速形成的电子能谱进行了模拟与分析. 固定入射激光束斑尺寸, 在(0.4-2)×1019/cm3等离子体密度范围, 对比分析了归一化峰值强度从1-6范围的激光脉冲在上述两种密度分布等离子 体中传输时激光束斑尺寸的演化, 结果表明抛物型分布的等离子体密度通道能够对超短超强脉冲实现良好的导引, 有利于高能电子加速. 对于较高密度情况,即使在均匀等离子体中依靠相对论自聚 焦等机制也可以实现良好的自导引传输,有利于实验简化以及产生更大电量的加速电子. 相似文献
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随着超短脉冲激光技术的发展, 人们可以在台面尺度获得光强超过1018W/cm2、脉宽小于100fs的超短脉冲激光.超短脉冲激光很容易把静止的电子加速到兆电子伏的能量. 而更重要的是超短激光脉冲可以通过其有质动力激发大振幅的等离子体波(称为激光尾波场), 后者可以在毫米空间尺度把电子加速到上百兆电子伏的能量.文章将介绍激光尾波场加速电子的物理机制和方案、这个领域的最新进展、以及目前存在的问题. 相似文献
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将门控分幅相机与平面晶体谱仪耦合,构成时间分辨光谱测量系统,对Al激光等离子体的K壳层发射谱进行测量,获得了相对入射激光延迟约1ns,积累时间约200ps的光谱信号。利用稳态碰撞-辐射平衡(CRE)近似条件下的等离子体光谱辐射动力学模型,给出了Al激光等离子体Ly-β线与He-β线强度比以及Ly-γ线与He-γ线强度比与电子温度的函数关系。在此基础上,根据实验谱线强度比,得到激光强度为2.319×1014,1.937×1014和3.946×1014 W/cm2时,等离子体冕区电子温度分别为1.190(1±27%),1.165(1±27%)和1.525(1±27%)keV。 相似文献
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报道了在20 TW皮秒激光器上完成的p偏振激光与等离子体相互作用过程中产生的快电子的角分布和能谱测量结果。实验得到:当激光功率密度小于1017 W/cm2时,电子发射没有明显定向性,在激光入射面内多峰发射;当激光功率密度大于1017 W/cm2,小于1018 W/cm2时,电子主要沿靶面法线方向发射;当激光功率密度达到相对论强度时,电子主要沿激光传播方向发射;激光功率密度未达到相对论强度时,靶后表面法线方向快电子能谱拟合平均温度符合共振吸收温度定标率;激光功率密度达相对论强度以上时,靶后表面法线方向快电子能谱拟合平均温度高于已有的温度定标率。 相似文献
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大气中的水汽对DF激光主要强线的吸收相对较小,而HF激光的大多数谱线受水汽和CO2分子等的吸收较大。利用较新的HITRAN96数据库和我国不同地区的气象资料,采用逐线积分法计算了HF/DF 激光的大气衰减情况。所选的谱线中,在合肥地区(年平均), HF的水汽吸收系数最大值可达到10km-1的数量级,二氧化碳吸收系数最大可达10-4~10-3km-1量级,P2(8)线吸收最弱;DF激光水汽吸收系数最大值可达到10-1km-1,比HF低2个量级,且随高度衰减很快,10km处就到10-5~10-4km-1量级,P2(8)线吸收最弱。在我国,由南向北,由夏季到冬季,水汽浓度减少,大气对HF/DF激光的吸收率也相应地递减。 相似文献
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用同一动能(150keV)而不同电荷态的40Arq+(8≤q≤16)离子入射金属Al表面,靶原子受激辐射产生特征光谱线. 实验结果表明:高电荷态离子与金属表面相互作用过程中,经过与靶原子碰撞(Penning碰撞)交换动能和共振电子俘获(resonant capture)释放库仑势能,将携带的能量沉积于靶表面,使靶原子激发. 这种激发不同于光激发,它不仅激发了原子复杂电子组态之间的跃迁,而且跃迁辐射的特征谱线强度增强的趋势与入射粒子的库 相似文献
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It is shown that stochastic heating can play an important role in Laser Wake Field Acceleration. When considering low density plasma interacting with a high intensity wave perturbed by a low intensity counterpropagating wave, stochastic heating can provide electrons with the right momentum for trapping in the wake field. The influence of stochastic acceleration on the trapping of electrons is compared to the one of cold injection by considering several polarizations of the colliding pulses. For some value of the plasma density and pulse duration, a transition from an injection due to stochastic acceleration to a cold injection dominated regime – regarding the trapped charge – has been observed from PIC code simulations. When the plasma density exceeds some value, stochastic heating becomes important and is necessary in some circumstances to get electrons trapped into the wakefield. 相似文献
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Laser wakefield accelerators(LWFAs)are compact accelerators which can produce femtosecond high-energy electron beams on a much smaller scale than the conventional radiofrequency accelerators.It is attributed to their high acceleration gradient which is about 3 orders of magnitude larger than the traditional ones.The past decade has witnessed the major breakthroughs and progress in developing the laser wakfield accelerators.To achieve the LWFAs suitable for applications,more and more attention has been paid to optimize the LWFAs for high-quality electron beams.A single-staged LWFA does not favor generating controllable electron beams beyond 1 Ge V since electron injection and acceleration are coupled and cannot be independently controlled.Staged LWFAs provide a promising route to overcome this disadvantage by decoupling injection from acceleration and thus the electron-beam quality as well as the stability can be greatly improved.This paper provides an overview of the physical conceptions of the LWFA,as well as the major breakthroughs and progress in developing LWFAs from single-stage to two-stage LWFAs. 相似文献
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Successive particle acceleration by use of two tightly focused ultra-short intense laser pulses
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We suggest a scheme of electron acceleration by use of two tightly focused ultra-short intense laser pulses at a 100TW level. Electrons obtain a preliminary acceleration with a small angular spread by the longitudinal ponderomotive force of the first pulse. They are then injected and further accelerated to hundreds of MeV by the second laser pulse. 相似文献
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The Linear Induction Accelerator (LIA) is a unique type of accelerator that is capable of accelerating kilo-Ampere charged particle current to tens of MeV energy. The present development of LIA in MHz bursting mode and the successful application into a synchrotron have broadened LIA's usage scope. Although the transformer model is widely used to explain the acceleration mechanism of LIAs, it is not appropriate to consider the induction electric field as the field which accelerates charged particles for many modern LIAs. We have examined the transition of the magnetic cores' functions during the LIA acceleration modules' evolution, distinguished transformer type and transmission line type LIA acceleration modules, and re-considered several related issues based on transmission line type LIA acceleration module. This clarified understanding should help in the further development and design of LIA acceleration modules. 相似文献
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Generation of fast protons in moderate-intensity laser-plasma interaction from rear sheath
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Forward fast protons are generated by the
moderate-intensity
laser--foil interaction. Protons with maximum energy 190~keV are
measured by using magnetic spectrometer and CR-39 solid state
track detectors along the direction normal to the rear surface.
The experimental results are also modeled by the particle-in-cell
method, investigating the time-varying electron temperature and
the rear sheath field. The temporal and spatial structure of the
sheath electrical field, revealed in the simulation, suggests that
these protons are accelerated by target normal sheath acceleration
(TNSA) mechanism. 相似文献
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《Current Applied Physics》2015,15(3):174-179
The acceleration of electrons by a plasma wave in the presence of density ripple in plasma has been investigated. Plasma density ripple can excite higher harmonics of different phase velocities of the fundamental plasma wave. The combined role of the different harmonics of the plasma wave contributes significantly in electrons energy gain during acceleration by the fundamental plasma wave. Our calculation shows that the plasma electrons gain considerable energy during the acceleration by the plasma waves in the presence of a density ripple in plasma. The initial electron energy and the ripple density play an important role for the acceleration of an electron. 相似文献
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Diego F.M. Oliveira 《Physica A》2010,389(5):1009-728
Some dynamical properties of a classical particle confined inside a closed region with an oval-shaped boundary are studied. We have considered both the static and time-dependent boundaries. For the static case, the condition that destroys the invariant spanning curves in the phase space was obtained. For the time-dependent perturbation, two situations were considered: (i) non-dissipative and (ii) dissipative. For the non-dissipative case, our results show that Fermi acceleration is observed. When dissipation, via inelastic collisions, is introduced Fermi acceleration is suppressed. The behaviour of the average velocity for both the dissipative as well as the non-dissipative dynamics is described using the scaling approach. 相似文献
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本文提出采用了强激光与细锥形靶作用, 产生大量定向高能电子, 用于快点火激光聚变方案研究. 通过PIC 模拟, 研究了细锥靶和激光脉冲的各项参数, 对产生高能电子的影响. 模拟发现, 细锥靶开口10° 时能够产生较多的高能电子, 当开口角度逐渐增大时, 高能电子的能量和数目都有一定程度下降. 若为细锥靶加上预等离子体, 产生的高能电子的数目将大大提高, 而最高的电子能量将会下降. 中等能量的电子加速主要由于激光有质动力加速, 而高能量的电子加速主要由于电子感应加速. 随着激光脉宽的增加, 高能电子的数量直线上升.
关键词:
细锥形靶
电子加速
感应共振加速 相似文献